Certain medical devices must be disassembled after each surgical procedure for purposes of inspection, cleaning and sterilization. For example, the handpiece of an ultrasonic aspirator must be disassembled and handled according to certain procedures in order to assure that it will be safe and sterile for the next surgical procedure. Often these surgical devices are expensive to replace. Therefore it is desirable to have simplified assembly and disassembly procedures in order to avoid damage due to mishandling. Also, a simplified assembly procedure will help assure that the equipment will be properly prepared for use in the operating room.
Repeated assembly and disassembly of a connector in a medical device will expose the connector to stress from possible overtorquing, particularly where threaded connections or the equivalent are used. The danger in exposing a medical device to high stress is that cracks may develop, which if not detected could pose a risk, e.g. malfunctioning equipment. This is particularly a problem where the connection must be fluid tight, as even small cracks may allow fluid to seep and pose a risk of injury to a patient.
Special tools can be used to prevent overtorquing, such as calibrated torque wrenches. However, these tools are subject to loss and becoming out of adjustment. Each special tool that is required for assembly of the medical device adds to the cost and complexity of the assembly procedure.
Another disadvantage of threaded connections is that the threads may become crossed during initial assembly. If not detected, cross-threading could result in the components not seating properly against each other. Where the attachment is to be fluid tight, poor seating represents a failure that might leak. Tactile feedback is often not available to let the assembler know when the members are properly seated.
Bayonet type connectors have been used to overcome some of the drawbacks of a threaded connectors in medical devices. U.S. Pat. No. 4,737,148 discloses a fluid T coupling comprising a through fluid flow path and an intersecting vent path. The vent path has a filter that is integrally molded with the bayonet connector to be received by an aspirator through path to control the level of vacuum communicated to an irrigation aspiration handpiece during eye surgery.
Patent application DE 2461271 discloses a surgical cannula with a sleeve arranged behind a needle end for connecting to an injection nozzle. The inner space of the sleeve has a connection section for forming a joint of the screw or bayonet type between the sleeve and the injection nozzle.
Patent application CH 632147 discloses a saliva extractor for use in a dental surgery having a suction body and pipe movably coupled together. The two can be arranged to engage together by a bayonet coupling or the pipe can be crimped or expanded at the end. No apparent sealing or resilient locking is apparent.
U.S. Pat. No. 4,494,555 has a surgical instrument for taking skin samples in which a barrel and an end fitting are connected by a bayonet coupling and a spindle and rotor sleeve are connected by a similar second bayonet coupling. This provides for easy disconnection of the barrel and end fitting, thus allowing the fitting and tool to be sterilized separately.
Gasket seals have also been used in connectors for medical devices, and in particular for connections where a fluid tight seal is desired. U.S. Pat. No. 3,076,904 discloses an acoustically vibrated material cutting and removing device which incorporates a gasket seal in a connection between a vibrator element and a tubular retainer. However, the gasket seal is not integral with a bayonet connector.
None of the disclosures above teaches the specific geometry of the present mechanism. In particular, none of the medical instruments disclosed above has a fluid tight bayonet connector which provides the additional features of tactile feedback and over torque protection by means of indexed rotation after seating.